This invention relates to a scroll compressor, and more particularly to a type thereof wherein sealing of a high pressure chamber formed between the movable scroll member and the frame can be substantially improved.
Recently, scroll compressors have been frequently used in refrigerators and the like. Referring to FIGS. 1 to 5, the scroll compressor comprises a stationary scroll member 1 and a movable scroll member 2 respectively having spiral wraps 1a and 2a of involute or the like configuration. The stationary scroll member 1 and the movable scroll member 2 are engaged with each other with a predetermined angle (180.degree.) maintained therebetween, so that a compressing space 3 of a crescent shape is formed between the wraps 1a and 2a. When the movable scroll member 2 is driven to move orbitally around the center O.sub.1 of the stationary scroll member 1 while maintaining a predetermined eccentric distance e, the compressing space 3 is moved toward the center of the spiroid spiral with the volume of the space 3 being reduced. As a consequence, the fluid in the compressing space 3 is continuously compressed and delivered from a central port (not shown) of the compressor.
FIGS. 3 and 4 illustrate a construction of a compressing element 4 of the scroll compressor, which has been disclosed in our copending U.S. patent application Ser. No. 655,429 (filed: Sept. 28, 1984). In the construction, the peripheral portion 5 of the stationary scroll member 1 is secured to a frame 6 by means of bolts 7 and the like, while the movable scroll member 2 engaging with the stationary scroll member 1 is encased in the frame 6 to be freely revolvable. The movable scroll member 2 has a rear side, which is opposite to the front side provided with the wrap 2a, supported by the frame 6 through a high-pressure receiving annular member 9.
The high-pressure receiving annular member 9 is mounted, as shown in FIG. 4, on a mounting surface 10 of the frame 6, and on the upper surface 11 of the member 9 is provided a high pressure chamber 12 for counter-balancing a thrust caused in the compressing element 4. A fluid passage 14 is formed through a planar portion 13 of the movable scroll member 2 for introducing the fluid extracted from the compressing space 3, or from the last stage of the compression, into the high pressure chamber 12. A bearing portion 15 is formed on the rear surface 8 of the movable scroll member 2 to be coupled with an eccentric shaft portion 17 of a crank shaft 16 rotatably supported by the frame 6. As a consequence, when the crank shaft 16 is rotated, the movable scroll member 2 is revolved around the center of the wrap 1a of the stationary scroll member 1. For preventing the rotation of the movable scroll member 2 around its own axis at this time, an Oldham ring 18 is provided between the movable scroll member 2 and the frame 6.
In the above described conventional construction of the compressing element 4, however, the sealing property of the sliding portion provided between the high-pressure receiving annular member 9 and the movable scroll member 2 has been comparatively low, and a relatively large amount of the pressurized fluid may be leaked out of the high pressure chamber 12. That is, when the pressurized fluid of a pressure Pd is supplied through the fluid passage 14 into the high-pressure chamber 12, a force Pm pushing the movable scroll member 2 upward is created in the chamber 12, thereby providing a gap S of a distance .DELTA.l.sub.1 between the high-pressure receiving annular member 9 and the rear-side surface 8 of the movable scroll member 2. Because of the provision of the gap S, the pressure of the fluid in the chamber 12 is reduced, thus making it difficult to provide a sufficient strength of force counter-acting against the thrust applied to the movable scroll member 2. Furthermore, since the leaked fluid has been extracted from the compressing space 3 or from the last stage of the compression, leakage of the same reduces the compression efficiency of the compression element 4.